Purpose: The objective of this proposal is to design randomized, controlled rnulticenter trials evaluating interventions to increase the survival of vascular access for hemodialysis and to form a collaborative network of clinical centers and a data coordinating center to perform such studies. Specific Aims: This application has two specific research aims: l) To determine whether the administration of clopidogrel for four weeks beginning on the day prior to native fistula creation reduces the rate of early fistula failure compared with placebo, and 2) To create a Collaborative Boston Area Clinical Center with the patient population and clinical and research expertise necessary to conduct the series of studies of the Hemodialysis Vascular Access Clinical Trials Consortium. Background: Maintenance of vascular access for hemodialysis is one of the major challenges in the care of the hemodialysis patient. Access-related problems are among the most frequent reasons for hospitalization in the end-stage renal disease (ESRD) population, and the cost of vascular access placement and repair in the United States currently exceeds $700 million per year. Despite the well-established advantages of native arteriovenous fistulae (higher unassisted potency rates and lower rates of infection) compared to grafts or catheters, the proportion of the United States hemodialysis population with a native fistula is low. An important factor contributing to this low prevalence is early thrombosis of newly created fistulae. Several small studies of antiplatelet agents have shown a reduction in early thrombosis rates of native fistulae, but have not been powered sufficiently to definitively demonstrate a benefit. Methods: Patients with chronic renal failure who are scheduled to undergo creation of a native fistula and are without contraindication to antiplatelet therapy will be randomized to receive either placebo or clopidogrel 75 mg daily beginning the day prior to fistula creation and continuing for an additional 4 weeks. The primary outcome measure will be attainment of a fistula suitable for dialysis without any radiologic or surgical intervention. The secondary outcome measures will be: l) fistula potency at completion of study drug, and 2) attainment of a fistula suitable for dialysis including those fistulae modified radiologically or surgically. The Boston Area Clinical Center will be comprised of five facilities with greater than 600 patients currently on hemodialysis and large pre-ESRD populations from which to draw study subjects. These study sites have extensive successful experience in multicenter clinical trials in ESRD. The Boston Area Clinical Center is organized to efficiently collaborate on the series of clinical trials conducted by the Hemodialysis Vascular Access Clinical Trials Consortium.